Single endless strand mounted in a series of parallel convolutions as a fibrous web supporting surface in a papermaking machine

ABSTRACT

A DYNAMIC PAPER WEB SUPPORTING STRUCTURE FOR A PAPERMAKING MACHINE IN WHICH CROSS DIRECTION ELEMENTS ARE EIMINATED. A SINGLE ENDLESS STRAND IS MOUNTED TO TRAVEL IN AN ENDLESS PATH OVER A SERIES OF ROLLS, AND ADJACENT MACHINE DIRECTION LOOPS OR CONVOLUTIONS OF THE ENDLESS STRAND ARE IN CLOSELY SPACED PARALLEL RELATION AND FORM A MOVING SUPPORTING SURFACE FOR THE PAPER WEB AND ADVANCE THE WEB THROUGH THE MACHINGE. DURING THE PAPERMAKING PROCESS BOTH WATER AND WATER VAPOR ARE EXTRACTED, WHILE THE PAPER SHEET IS BEING FORMED, PRESSED AND DRIED. ALTERNATE CONVOLUTIONS OF THE SINGLE ENDLESS STRAND CAN BE SEPARATED FROM THE SUPPORTING SURFACE AND PASSED IN ANGULAR CONTACTING RELAION WITH EACH OTHER FOR CLEANING PURPOSES. A PIVOTABLE COMB CAN ALSO BE EPLOYED IN CONTACT WITH THE STRAND CONVOLUTIONS OUTSIDE THE SUPPORTING SURFACE TO ADJUST THE SPACING THEREBETWEEN.

3,814,665 SINGLE ENDLESS STRAND MOUNTED IN A SERIES OF PARALLEL J1me 1974 F. H. ORBISON E AL CONVOLUTIONS AS A FIBROUS WEB SUPPORTING SURFACE IN A PAPERMAKING MACHINE Original Filed Feb. 11, 1970 2 Sheets-Sheet 1 Attorneys June 4, 1974 F. H. ORBISON ETAL 3,814,665 SINGLE ENDLESS STRAND MOUNTED IN A SERIES OF PARALLEL CONVOLUTIONS AS A FIBROUS WEB SUPPORTING SURFACE IN A PAPERMAKING MACHINE Original Filed Feb. 11, 1970 2 Sheets-Sheet 2 INVENTORS FRANK H. ORBISON Attorneys WOWARD M HELLAND United States Patent US. Cl. 16227 4 laims ABSTRACT OF THE DISCLOSURE A dynamic paper web supporting structure for a papermaking machine, in which cross direction elements are eliminated. A single endless strand is mounted to travel in an endless path over a series of rolls, and adjacent machine direction loops or convolutions of the endless strand are in closely spaced parallel relation and form a moving supporting surface for the paper web and advance the web through the machine. During the papermaking process both water and water vapor are extracted, while the paper sheet is being formed, pressed and dried. Alternate convolutions of the single endless strand can be separated from the supporting surface and passed in angular contacting relation with each other for cleaning purposes. A pivotable comb can also be employed in contact with the strand convolutions outside the supporting surface to adjust the spacing therebetween.

This application is a continuation of application Ser. No. 10,412, filed Feb. 11, 1970, now abandoned.

This invention relates to a porous supporting structure for a fibrous web or sheet containing a fluid impregnant and more particularly to a supporting structure to support and advance a paper web through a papermaking machine.

In a papermaking machine diluent water used to prepare cellulose fibers for sheet formation must be removed and the water carried by the formed sheet must be extracted, and most of the water absorbed by the pressed sheet must be driven out by heat in order to create a paper product. While these water removing operations are taking place, the paper web or sheet must be supported and conveyed by a structure which satisfies the water removal requirements. Since gravity, vacuum, pressure absorption and vaporization are successively used to control the appropriate rate of maximum water removal and also to satisfy the finish or smoothness requirements of the sheet, the structures which support and convey the paper web control the success of the papermaking operation.

The papermaking machine has three sections: forming, pressing and drying. Each section has distinctive supporting and conveying structures which provide different water removing rates and different paper surface smoothness influences in order to simultaneously provide for the imposed process and product requirements described above. The structures used to support and convey the paper web in each of these sections are respectively, Fourdrinier Wires or forming fabrics, wet felts and dryer felts.

Each of these distinctive structures has functional and practical shortcomings. Metal wires wear, or because of their fragile structure, become damaged, resulting in frequent and costly replacement. Wet felts become plugged with foreign materals and fail to drain the water being pressed from the formed sheet at a sustained high rate, thereby also resulting in frequent and costly replacement. Dryer felts are basically inefficient because the vaporized water is trapped by the fabric itself resulting in a return to the sheet of the released water vapor.

The presence in each of these structures of both machine direction elements, or warp yarns, and cross direction elements limits their effectiveness in the primary function which is water removal. If cross direction elements were eliminated, a sustained maximum water removal rate would be assured because neither water nor water vapor could be dammed or trapped since it could always flow unrestricted between the machine direction elements. Furthermore, the wear of wires would be reduced since the cross direction elements cause the machine direction elements to assume a generally zig-zag or corrugated configuration and the knuckles or points of junction of the elements strike against cross direction components of the papermaking machine which causes wear at the knuckles. The elimination of cross-direction elements would also minimize the plugging of wet felts since there would be no holes or pockets to plug up and would improve the efliciency of dryer felts because the vapor would not be trapped in the fabric since exhaust channels would be present.

Accordingly, the invention is directed to a supporting structure for a paper web or sheet in which the cross direction elements are eliminated and a single endless strand is arranged in a series of machine direction loops or convolutions and serves to support the paper web during each of the papermaking processes. As the single strand can be varied in composition, structure, size and spacing, it can be substituted for and improve upon any of the three basic supporting and conveying structures conventionally used in papermaking machines.

More specifically, the web supporting structure of the invention is composed of a single endless element or strand which is mounted to travel over a series of rolls in an endless path. The path of travel is arranged so that portions of adjacent turns or convolutions of the strand move in the machine direction and are in closely spaced parallel relation and form a moving supporting surface or table which serves to support the paper web and advance the web through the sections of the papermaking machine. As a feature of the invention, each alternate convolution can be separated from adjacent convolutions after leaving the supporting surface and subsequently passed in angular contacting relation to the adjacent convolutions at a lease area. The lease serves a multiple function of not only controlling the sequence of consecutive convolutions but also, due to the contact between adjacent convolutions, provides a self-cleaning action and automatically spaces the individual convolutions.

The use of the single endless strand to form the web supporting surface provides substantial advantages over the normal supporting structure, such as a conventional Fourdrinier wire, wet felt or dryer felt. As the cross direction elements or yarns are eliminated, sustained maximum water removal is achieved, for the Water or water vapor can pass freely between the machine direction elements without interference from cross direction elements.

As an additional advantage, the lateral spacing between the machine direction convolutions in the supporting surface can be readily adjusted to meet specified paper finish requirements. Moreover, by increasing the lateral spacing between convolutions in a non-operating zone, a cleaning effect is achieved which acts to dislodge foreign material located between adjacent convolutions.

Conventional felts or fabrics can be damaged and if, for example, a hole is punched in the fabric the value of the fabric is destroyed and it must be replaced, resulting in considerable downtime for the machine. Similarly, if a forming wire becomes bent or dented, excessive wear will normally occur at the bent area which reduces the service life of the forming wire and requires downtime of the machine for removal and replacement. The use of the single endless strand overcomes these problems for the strand can be replaced, if damaged or worn, without materially interrupting the continuity of the papermaking process. The machine can be momentarily shut down, the strand severed, and a new strand attached to the severed end. As the strand travels through the series of passes or convolutions, the new strand will be drawn through the desired pattern on the roll assembly so that the new strand can be substituted for the old strand without materially shutting down operation of the machine. As an alternate procedure, it may be possible, in some cases, to sever a portion of the strand which is in a non-operating position while the machine is in operation and attach a new strand to the severed end as the strand is moving through its path of travel.

As a further advantage, it is possible to perform desired operations on the strand outside of the web supporting area. For example, in a non-operating zone the strand can be subjected to treating operations, such as sizing treatments, lubrication, cleaning and the like. This enables the strand to be treated during normal operation without downtime for the machine.

The use of the single endless strand has a further important advantage in that the web supporting structure can be fabricated in situ rather than being prefabricated and shipped to the papermaking plant. A Fourdrinier wire, in particular, is fragile and extreme care must be taken during handling and transporting to prevent damage. However, with the invention, the strand is shipped in spool or coiled form and at the site of the papermaking machine the coiled strand is merely fed through the machine in the desired path of travel. This greatly simplifies the handling and transporting requirements.

The invention also simplifies the design of the papermaking machine itself. In the conventional forming and press sections the side of the papermaking machine must be constructed so as to be opened in order to be able to install and remove the endless forming wire or felt. The present invention eliminates the need of the side of the machine being opened because the strand can be merely fed through the rolls in the desired pattern.

Other objects and advantages will appear in the course of the following description.

The drawings illustrate the best mode presently contemplated of carrying out the invention.

In the drawings:

FIG. 1 is a schematic representation of a Fourdrinier papermaking machine utilizing the web supporting structure of the invention;

FIG. 2 is a diagrammatic view of the press section of the papermaking machine;

FIG. 3 is a diagrammatic view showing the path of travel of the strand in the press section;

FIG. 4 is a fragmentary plan view of a reed or comb employed in the structure of FIG. 2; and

FIG. 5 is a perspective view of the intersection of convolutions at a lease area.

FIG. 1 illustrates diagrammatically a papermaking machine including a Fourdrinier section 1, a press section 2, and a dryer section 3. The Fourdrinier section includes a headbox 4 which supplies a slurry of paper pulp through a slice 5 onto a web supporting surface 6 to form a paper web or sheet 7. The supporting surface 6 is formed by a single endless strand 8 which is wound around a roll assembly so that the adjacent machine direction convolutions of the strand are in closely spaced parallel relation and define the moving supporting surface 6.

In forming, a very dilute suspension of fibers is extruded onto the freely draining surface 6 which acts as a filter, collecting the fibers in a wet mat and permitting free passage of water between the machine direction ele- 4 ments or convolutions. Thus, the forming surface must filter fibers from the suspension and drain away excess amounts of water, while at the same time it supports and transports the web of loose fibers which have built up upon its surface. To do this effectively, the supporting surface 6 should be relatively open with uniform spacing between adjacent convolutions of the strand. Preferably, to provide free drainage, the strand is impermeable, and may be formed of metal wire; monofilament plastic, such as nylon, polyester or polyacrylic; or plastic impregnated or non-impregnated textile yarn or braid formed of natural or synthetic fibers or blends of the two.

The roll assembly which supports the strand 8 includes a breast roll or guide member 9 located beneath the slice 5, and the slurry, which is discharged through the slice onto the supporting surface 6, is carried over a plurality of table rolls 10. As the paper web 7 passes over the table rolls or guide members 10, a portion of the water in the web is removed and passes through the spaces between adjacent convolutions of the strand 8.

As the web is further advanced by the supporting surface 6 of the endless strand 8, it may be subjected to the action of a series of dewatering foils 11, followed by a series of suction boxes 12 which also act to remove a portion of the water from the web. A third sequence of water removal may also be provided by a driven guide member or couch roll 13 having a suction gland ex tending the length thereof. Negative pressure applied to the suction gland also serves to extract water from the web.

The roll assembly of the Fourdrinier section also includes a series of guide rolls 14 which are located in planes beneath the table rolls 10.

The strand 8 may be driven in its endless path by any conventional drive mechanism. As shown diagrammatically in FIG. 1, a motor and transmission unit 13a is connected to the shaft 13]) of roll 13 and serves to drive the roll 13, thereby driving the strand in its path of travel.

To provide the endless path of travel for the strand 8, the convolution at one side edge of the pattern passes upwardly from the breast roll 9 over a pulley or guide 15, then moves horizontal to the opposite side of the machine where it passes downwardly around a pulley or guide 16 and reenters the pattern.

Following the forming section, the web 7 is delivered to the press section 2 and the invention is described in detail with respect to the press section. Pressing is the operation of wringing or extracting water from the wet fiber web by passing the web through a set of coacting press rolls. The web 7 is conveyed on a supporting structure which serves to (1) support the weak web within the pressure zone, (2) uniformly compress the wet web so as to obtain maximum pressing efliciency and sheet smoothness, (3) receive water expressed from the web, and (4) transfer water away from the pressure zone.

As best illustrated in FIG. 2, the press section 2 includes a pair of press rolls 17 and a single endless strand 18, similar to strand 8, is arranged to travel over a roll assembly with convolutions of the strand travelling in the machine direction and being located in closely spaced parallel relation to define a web supporting structure located between the press rolls 17 and indicated by 19. The paper web or sheet 7 is delivered or supplied to the press section 2 by the forming section 1, and as the Web passes between the coacting press rolls 17 while supported on the surface 19, water is extracted or removed from the web.

The convolutions of the strand 18 at the supporting surface 19 should he contiguous or relatively close together so as to provide maximum uniformity of support and pressure application. Furthermore, the strand should be permeable so as to accommodate water expressed from the paper web, compressible so as to respond to the pressure zone and apply uniform pressure, and resilient so as to recover from the pressure zone and continually provide voids for accepting expressed water. In a pressing application the surface 19 is visualized as having contiguous strands which when pressed in the nip zone conform to the nip geometry. It has been found that textile yarns composed of either natural or synthetic fibers, or blends of the two, in the form of continuous yarns or braided or twisted structures provide these desired characteristics and are particularly satisfactory for use as the strand 18 in the press roll section 2.

As illustrated in FIG. 2, each alternate convolution or loop of the strand 18 is separated from adjacent convolutions on leaving the nip zone and passes downwardly around the roll 20 to roll 21, while the adjacent convolutions travel around the roll or guide member 22, and are reunited with the alternate convolutions at the roll 21. The convolutions are again separated with each alternate convolution passing upwardly around the roll or guide member 23 and back to the nip zone between the press rolls 17, while the adjacent convolutions travel over the roll 20 and are again reunited with the alternate convolutions at the nip zone. The group of convolutions passing downwardly from the press roll 17 to the roll 20 crosses or passes in angular contacting relation with the group of convolutions moving upwardly from the roll 20 to the press roll 17, at a lease indicated by 24. Similarly, the group of convolutions traveling from roll 20 to roll 21 crosses the group of convolutions traveling from roll 21 to roll 20 at a lease area 24a. Thus, the manner in which the strand 18 is wound on the roll assembly provides a means for separating the path of travel of each alternate convolution from the path of travel of adjacent convolutions and a means for passing the alternate convolutions in angular contacting relation at lease areas 24 and 24a to the adjacent convolutions. The action between adjacent convolutions at the lease areas 24 and 24a serves a multiple function. It not only controls the sequence of consecutive convolutions but also, due to the doctoring or stripping action, provides a self-cleaning effect for the strand and automatically spaces the individual convolutions.

To provide precise lateral spacing of the convolutions in the area of the supporting surface 19 at the nip zone, a series of combs or reeds 25 can be utilized. Each comb 25 includes a series of slots or teeth 26 to receive the individual convolutions and serves to accurately space the convolutions apart. The various groups of convolutions both approaching and leaving the area of the supporting surface 19 pass within teeth 26 of combs 25 so that the adjacent convolutions in the supporting surface 19 are precisely spaced or aligned. To vary the lateral spacing of the convolutions in the supporting surface 19, the combs 25 can either be of a pivotable or adjustable type or combs having different tooth spacing can be employed. FIG. 4 illustrates a pivotable type of comb which can be utilized to vary the lateral spacing of the convolutions. As shown in FIG. 4, the comb 25 is supported by a shaft 38 which is journalled within a bushing 39 in the frame 40 of the machine. The shaft 38 and comb 25 can be locked against rotation by a nut 41 which is threaded on the outer end of the shaft. By loosening the nut 41, the shaft and comb can be pivoted or adjusted in angularity to thereby vary the lateral spacing of the convolutions passing within the teeth 26 of the comb. By varying the lateral spacing of the convolutions in the supporting surface 19, the finish characteristics of the paper can be varied.

In addition, adjustment of the pivotable combs 25 in a non-operating zone can selectively increase or decrease the lateral spacing between adjacent convolutions and thereby aid indislodging any foreign particles which may be lodged between convolutions. For example, increasing the lateral spacing between adjacent convolutions in a single plane, or separating alternate convolutions into different planes can serve to dislodge contamination between adjacent convolutions.

The combs 25 also act to prevent lateral displacement of the convolutions due to the fact that the strand is displaced laterally the width of one convolution each time the strand completes a revolution around the roll assembly. This function can also be accomplished by mounting a freely pivotable roll in the roll assembly so that the pivotal action automatically tends to deflect the convolution laterally in a direction opposite to the normal displacement.

FIG. 3 illustrates, in diagrammatic form, the path of travel followed by the strand in the structure shown in FIG. 2. As shown in FIG. 3, the strand travels from the roll 23 to the press roll 17 in a path 18a and as the strand passes over press roll 17 it constitutes a portion of the web supporting structure 19. The strand then passes downwardly as indicated by 18b around the roll 22 to the roll 21 in a path 180. The strand passes upwardly around the roll 12 in path 18d, around the roll 20 and back up to the press roll in a path indicated by 182. The portion of the convolution located on the press roll 17 also constitutes a portion of the web supporting structure 19. After leaving the press roll 17 the strand passes downwardly in path 18 around the roll 20 and to the roll 12 in the path 18g. After traveling around the roll 21, the strand passes upwardly in path 18h around the roll 23 and back toward the press roll in path 181, which is parallel to path 18a and also functions as a portion of the web supporting structure 19. The strand then passes from the press roll 17 to the roll 22 in a path 18 around the roll 22 and downwardly along path 18k to the roll 21. After passing beneath the roll 12 the strand passes around the pulleys 27 and 28 and reenters the pattern in the path 18a.

While FIG. 3 shows the convolutions at the supporting area 19 to be a considerable distance apart, in practice these convolutions would be in closely spaced relation. Moreover, while FIG. 3 illustrates only three convolutions utilized as a portion of the supporting surface 19, in practice, there may be hundreds or thousands of adjacent convolutions disposed in closely spaced parallel relation which define the web supporting surface.

While the web supporting surface 6 in the forming section 1 supports the paper web or sheet 7 over a considerable distance, the web supporting surface 19 in the press section 2 may be in contact with the sheet 7 only in the area of the nip zone between the press rolls 17.

The winding pattern of strand 18, as illustrated on FIGS. 2 and 3, is not critical to the invention and various winding patterns can be utilized for the endless strand, including patterns with or without lease areas and with or without the separation of alternate convolutions from adjacent convolutions during various portions of the path of travel.

The single strand concept is also employed in the dryer section 3. The drying operation entails driving oif moisture in the wet web or sheet 7 by means of heat energy. The dryer section 3, as shown in FIG. 1, includes a series of heated upper dryer rolls 29 and lower dryer rolls 3'0 and the paper web 7 passes successively over the rolls 29 and 30. A single endless strand 31 similar to strand 18 travels over a series of rolls 32 and adjacent machine direction convolutions of the strand serve as a supporting structure for the paper web and apply uniform pressure against the upper dryer rolls 29 to increase heat transfer from the dryer rolls to the paper web. The paper web 7 is supplied to the dryer section 3 by the press section 2, and as the web passes over the dryer rolls 29 and 30 the moisture in the web is driven off to dry the web.

The strand 18 can be driven in its path of travel by any conventional drive mechanism. As shown diagramatically in FIG. 1, a motor and transmission unit 29a is connected to the shaft 29b of one of the rolls 29 and serves to rotate the roll and thereby move the strand in its endless path of travel.

To provide the endless pattern for strand 31, the convolution at one side edge of the supporting structure passes over a guide 33, then travels horizontally to the opposite side edge of the supporting structure where it travels over a guide 34 and reenters the pattern in the manner previously described.

In this application the convolutions of the strand should be relatively close together to provide maximum heat transfer and the strand itself may be permeable or impermeable depending upon the volume to be handled.

In addition to the strand 31, a second endless strand 35 is wound over a series of rolls 36 to provide a second supporting structure for the paper web. The adjacent machine direction turns or convolutions of strand 35 are in closely spaced relation and serve to apply uniform pressure against the surface of the lower drying rolls 30 to maximize heat transfer.

To provide the endless pattern for the strand 35, the convolution at the side edge of the supporting structure passes over guides or pulleys 37, travels horizontally to the opposite side of the machine where it passes over a second pulley, not shown, and re-enters the pattern in the manner previously described.

Elimination of the cross direction elements in dryer fabrics has an advantage in drying as a means to reduce air pumping which occurs in drying sections equipped with open mesh dryer fabrics. Large volumes of air trapped within the interstices may produce sheet flutter or instability when the machine is operated at high speed.

The use of a single endless strand for forming a moving supporting surface for the paper web is a novel and unique concept. The elimination of cross direction elements from the supporting surface provides distinct advantages in that it improves the extraction of water and water vapor, as well as providing a more uniform fish for the paper and enabling the structure to be more readily cleaned without downtime of the machine.

Various modes of carrying our the invention are contemplated as being within the scope of the following claims particularly pointing out and distinctly claiming the subject matter which is regarded as the invention.

We claim:

1. A structure for supporting and advancing a web impregnated with a fluid, comprising a guide assembly, a strand, means for mounting the strand for travel on the guide assembly in a series of repeating generally parallel convolutions with portions of said convolutions being in substantially continguous relation and disposed in a common plane and defining a web supporting surface consisting solely of machine direction elements, said sup-- porting surface disposed to support a fluid impregnated web, said guide assembly being a portion of the press section of a papermaking machine, and said strand being formed of a compressible, resilient, water-permeable material, means for removing fluid from the web as it is supported on the supporting surface, drive means for driving the strand in said path of travel to thereby move the supporting surface and the web supported thereby, means located outside of the supporting surface for separating the path of travel of each alternate convolution from the path of travel of adjacent convolutions, and means for passing said alternate convolutions in angular contacting relation to said adjacent convolutions at a location outside of said supporting surface to thereby clean the strand.

2. The apparatus of claim 1, and including means for reuniting the path of travel of said alternate convolutions with the path of travel of said adjacent convolutions.

3. The structure of claim 1, and including means located outside of said supporting surface for selectively increasing and decreasing the lateral spacing between adjacent convolutions to thereby aid in dislodging foreign material from between adjacent convolutions.

4. The structure of claim 1, and including a pair of cooperating pressure rolls acting against the portion of the web supported on said supporting surface to thereby extract fluid from the web.

References Cited UNITED STATES PATENTS 1,767,905 6/1930 Walker 210213 X 3,097,413 7/1963 Draper 162-358 X 2,296,897 9/1942 Billing et al. 198-190 X 2,987,988 6/1961 Robledano 198-190 X 3,570,653 3/1971 Cullen 198--190 3,417,488 12/1968 McCoy 198190 X 2,378,113 6/1945 Van de Carr, Jr. 162--206 X FOREIGN PATENTS 634,224 3/ 1950 Great Britain 198190 S. LEON BASHORE, Primary Examiner R. H. TUSHIN, Assistant Examiner US. Cl. X.R.

15104.51; 34-423, 162, 236; -118; 162-348, 354, 358, Dig. 1; 198-129, 190, 230; 226-470 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Petent No. 3, 14. 5 Dat d June '4. 1974 FRANK H. ORBISON and HOWARD M. HELLAND Inventor(s) It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 7 line 33 Cancel "fish" and substitute therefor -finish--- Signed and sealed this 17th day of September 1974.

(SEAL) Attest:

McCOY M. GIBSON JR. c. MARSHALL DANN Commissioner of Patents Attesting Officer FORM PO-1050 (10-69) USCQMM-DC wan-P09 fi U.S. GOVERNMENT PRINTING OFFICE 1"] 05i6-8J4, 

